1. Field of the Invention
This invention relates to a printing device for performing the printing operation for each page.
2. Description of the related art
In an ordinary page printer, an printing pattern is formed based on control data of one page supplied from an external host computer and a printing section is driven according to the printing pattern. The control data of one page includes character codes for specifying characters (numeral or symbol), attribute information for specifying the style, height and rotation of the character, and layout information for specifying the size of printing paper, a vertical motion index corresponding to the number of pitches of a line space and a horizontal motion index corresponding to the number of pitches between characters. The layout information and attribute information are used when it is required to change the contents of the specified printing conditions.
The conventional page printer includes a working RAM, a vector font memory, and a page memory to form a printing pattern. The working RAM is used to temporarily store control data of one page, various operation data and the like, and the vector font memory is used to previously store various vector fonts for representing various characters in the vector form. Further, the page memory is used to store bit map fonts representing various characters in the dot matrix form.
In forming the printing pattern, the working RAM and page memory are first initialized, and then control data is received. The control data is stored in the working RAM, and then it is checked whether or not the control data is the character code. When it is detected that the control data is the character code, the vector font memory is searched for the vector font of a character corresponding to the character code, and the vector font is read out from the vector font memory into the working RAM. Then, the vector font is subjected to the processing operation specified by the attribute information allotted to the character code so as to be converted or developed into a corresponding bit map font. The bit map font thus obtained is stored into that area of the page memory which is specified by the reception order of the character code and the layout information allotted to the character code. The printing pattern is formed by converting or developing the vector font corresponding to character codes of one page into the bit map font and storing the bit map font into the page memory.
The processing operation for converting the vector font into the bit map font generally includes 3-order floating decimal point multiplication, operation of trigonometric function, 2-dimensional matrix operation, operation for blackening the internal area of the font character, and the like. Since the processing operations are effected for all the vector fonts corresponding to the character codes of one page, a relatively long time is required to effect the processing operations. Therefore, it is impossible to start the printing operation immediately after the control data is received in the conventional page printer.
The method of converting the vector font into the bit map font is disclosed in the article by Foley and Van Dam, "Fundamentals of Interactive Computer Graphics", Addison Wesley Co. 1982, ISDN U-201-14468-9.